Morne Morkel returned with a five-wicket haul to clean up the Australian line-up in morning before Graeme Smith scored a century to lead the South African reply at Adelaide on Friday.

Adelaide: Graeme Smith survived two close calls to post his 26th Test century and guide South Africa's comeback Friday after Morne Morkel's five-wicket haul swiftly stemmed Australia's run flow in the second cricket Test.

South Africa reached stumps at 217-2 on day two in reply to Australia's first innings of 550, with Smith unbeaten on 111 and Jacques Rudolph on 25. The tourists were in a radically better position than they were at stumps the previous day, when Australia posted its second-highest first-day score of 482-5.

Morkel triggered Australia's tailend collapse when he bowled Michael Clarke for 230 and finished with 5-146. The Australians added only 68 in 21 overs before being dismissed just before lunch on Friday.

Australia resumed day two at 482-5 and added only 68 in 21 overs in ideal batting conditions, with Morkel bowling Michael Clarke (230) to spark South Africa's comeback.

Smith (57 not out) and Alviro Petersen (47 not out) shared an unbroken 117-run opening stand, surviving four overs before lunch and another 31 in the middle session.

Smith had a big reprieve on 46 when he stepped down the pitch and wicketkeeper Matt Wade missed a routine stumping chance off Clarke's part-time spin.

After a remarkable opening day, Friday hasn't been a good one for Clarke's Australians.

The hosts lost five wickets for 22 runs — including the dismissal of Mike Hussey on the last ball of the first day — slipping to 504-9 before James Pattinson (42) and Nathan Lyon (7 not out) combined for a 46-run last-wicket stand.

The slide started with the dismissal of captain Clarke, who became the first batsman to post four 200-plus test scores in one calendar year when he reached his double century late on day one. He added only six to his overnight score before he was beaten by Morkel and lost his middle stump. That dismissal ended his stunning start to the series against top-ranked South Africa, scoring 489 runs before losing his wicket — the 31-year-old Clarke scored an unbeaten 259 in the drawn first test at Brisbane last week.

Rory Kleinveldt collected his first test wicket — albeit after a very close review for a front-foot no-ball — when Peter Siddle (6) edged him to Smith at first slip.

Pattinson went out swinging and played an entertaining cameo just when it seemed Australia had completely lost its ascendancy, stroking four boundaries and two sixes in his 35-ball knock before he edged Dale Steyn to first slip, giving Smith his fourth catch of the innings.

The second morning contrasted sharply with the opening day, when the batsmen flayed a depleted South Africa attack for 66 boundaries and nine sixes and posted Australia's second-highest first day score ever. Clarke, Dave Warner (119) and Mike Hussey (103) were all punishing any wayward deliveries.

Legbreak bowler Imran Tahir was particularly punished and returned 0-180 from 23 overs — the ninth worst figures ever in test cricket. The 33-year-old Tahir's economy rate of 7.82 an over was the fourth worst of all time.

The South African attack had a massive setback when 37-year-old allrounder Jacques Kallis injured his right hamstring after taking two early wickets and limped off the field in the 17th over. Australia at that stage was 77-3. Kallis hasn't returned to the field and will not bowl in the remainder of the Adelaide test, but is expected to bat down the order.

His injury came only hours after paceman Vernon Philander was ruled out of the match with a bad back.